Method and apparatus for processing video pictures, in particular for large area flicker effect reduction

Abstract

The invention relates to a method and apparatus for processing video pictures, in particular for large area flicker effect and false contour effect reduction. This method concerns a new coding called Parallel Peak Coding. The general idea of the Parallel Peak Code is to have almost always the same energy in two packets of light and to encode the code words for these two packets differently so that changes in sub-field code word will not appear in the two packet code words simultaneously.

1 . Method for processing video pictures consisting of pixels, the pixels being digitally coded, the digital code word determining the length of the time period during which the corresponding pixel of a display is activated, wherein to each bit of a digital code word a certain activation duration is assigned, hereinafter called sub-field, the sum of the duration of the sub-fields according to a given code word determining the length of the time period during which the corresponding pixel is activated, the sub-fields of a pixel being organised in two consecutive groups such that to a value of a pixel a code word is assigned which distributes the active sub-field periods equally over the two sub-field groups, 
 wherein substantially all the sub-fields of the two groups have different activation durations and, for all pixel values apart from exceptions in the low pixel value range up to a first predetermined limit and/or in the high pixel value range from a second limit on, the pixel value is split into first and second substantially equal values, said first and second values being encoded into first and second code words, said first code word being the part of the code word assigned to one of the two sub-field groups and said second code word being the part of the code word assigned to the other sub-field group.    
   
   
       2 . Method according to  claim 1 , wherein a dithering step is applied to said first and second values before being encoded into first and second code words.  
   
   
       3 . Method according to  claim 1 , wherein, for a video pictures sequence with an increased frequency, the pixel values of the even pictures of the sequence are encoded into code words using one of the two sub-field groups and the pixel values of the odd pictures of the sequence are encoded into code words using the other sub-field group.  
   
   
       4 . Apparatus for processing video pictures consisting of pixels, the pixels being digitally coded, the digital code word determining the length of the time period during which the corresponding pixel of a display is activated, wherein to each bit of a digital code word a certain activation duration is assigned, hereinafter called sub-field, the sum of the duration of the sub-fields according to a given code word determining the length of the time period during which the corresponding pixel is activated, the sub-fields of a pixel being organised in two consecutive groups such that to a value of a pixel a code word is assigned which distributes the active sub-field periods equally over the two sub-field groups, 
 wherein substantially all the sub-fields of the two groups have different activation durations and encoding means are provided for splitting, for all pixel values apart from exceptions in the low pixel value range up to a first predetermined limit and/or the in the high pixel value range from a second limit on, each of said pixel values into first and second substantially equal values and encoding said first and second values into first and second code words, said first code word being the part of the code word assigned to one of the two sub-field groups and said second code word being the part of the code word assigned to the other sub-field group.    
   
   
       5 . Apparatus according to  claim 4 , wherein it further comprises dithering means for processing said first and second values.  
   
   
       6 . Apparatus according to  claim 4 , wherein, for a video pictures sequence with an increased frequency, the encoding means encode the pixel values of the even pictures of the sequence into code words using one of the two sub-field groups and the pixel values of the odd pictures of the sequence into code words using the other sub-field group.